Until very recently, the source of a wide variety of natural products was the native host. For the most part, proteins, particularly factors, were isolated from blood obtained from donors. The blood could be used for transfusions, providing a source of red blood cells. In addition, numerous blood factors which were extracted were used in the treatment of a host of diseases, such as hemophilia, thallasemia, other globin diseases, and the like. In many instances, particularly during surgery, the infusion of platelets is desirable. In cases of cancer of the bone marrow, there is substantial interest in being able to replace the neoplastic bone marrow with normal bone marrow.
Because of the central role that the hematopoietic system plays, there are frequent needs for the use of one or more of the hematopoietic lineages in the treatment of a patient. Furthermore, immature hematopoietic cells may serve in the investigation of the amplification, differentiation, and maturation of hematopoietic cells. Allogeneic stem cells may serve in the production of mature cells in a host deficient in one or more lineages or in stem cells. There is, therefore, substantial interest in being able to produce hematopoietic cells.